Automatic identification (“Auto-ID”) technology is used to help machines identify objects and capture data automatically. One of the earliest Auto-ID technologies was the bar code, which uses an alternating series of thin and wide bands that can be digitally interpreted by an optical scanner. This technology gained widespread adoption and near-universal acceptance with the designation of the Universal Product Code (“UPC”)—a standard governed by an industry-wide consortium called the Uniform Code Council. Formally adopted in 1973, the UPC is one of the most ubiquitous symbols present on virtually all manufactured goods today and has allowed for enormous efficiency in the tracking of goods through the manufacturing, supply, and distribution of various goods.
However, the bar code still requires manual interrogation by a human operator to scan each tagged object individually with a scanner. This is a line-of-sight process that has inherent limitations in speed and reliability. In addition, the UPC bar codes only allow for manufacture and product type information to be encoded into the barcode, not the unique item's serial number. The bar code on one milk carton is the same as every other making it impossible to count objects or individually check expiration dates, much less find one particular carton of many.
Currently, retail items are marked with barcode labels. These printed labels have over 40 “standard” layouts, can be mis-printed, smeared, mis-positioned and mis-labeled. In transit, these outer labels are often damaged or lost. Upon receipt, the pallets typically have to be broken-down and each case scanned into an enterprise system. Error rates at each point in the supply chain have been 4-18% thus creating a billion dollar inventory visibility problem. However, Radio Frequency Identification (RFID) allows the physical layer of actual goods to automatically be tied into software applications, to provide accurate tracking.
The emerging RFID technology employs a Radio Frequency (RF) wireless link and ultra-small embedded computer chips, to overcome these barcode limitations. RFID technology allows physical objects to be identified and tracked via these wireless “tags”. It functions like a bar code that communicates to the interrogator automatically without needing manual line-of-sight scanning or singulation of the objects.
The use of RFID tags are also quickly gaining popularity for use in the monitoring and tracking of an item. RFID technology allows a user to remotely store and retrieve data in connection with an item utilizing a small, unobtrusive tag. As an RFID tag operates in the radio frequency (RF) portion of the electromagnetic spectrum, an electromagnetic or electrostatic coupling can occur between an RFID tag affixed to an item and an RFID interrogator. This coupling is advantageous, as it precludes the need for a direct contact or line of sight connection between the tag and the interrogator.
Utilizing an RFID tag, an item may be tagged at a period when the initial properties of the item are known. For example, this first tagging of the item may correspond with the beginning of the manufacturing process, or may occur as an item is first packaged for delivery. Electronically tagging the item allows for subsequent electronic exchanges of information between the tagged item and a user, wherein a user may read information stored within the tag.
RFID tags may backscatter when even the smallest incoming signal is detected. Accordingly, where there are many tags in the vicinity of the interrogator, the interrogator is required to singulate and query each RFID tag in order to find a desired tag. In dock door or warehouse situations, where there are many readers and potentially hundred of thousands of tags, the processing time required to find a particular tag can be substantial. In most applications involving RFID, speed is a desirable characteristic. It would therefore be desirable if RFID tags could be set to selectively respond based on an interrogator signal strength.